(a) Field of Invention
The present invention relates to a display device, and more particularly, to a display device in which a reflective film is formed on walls of the display, thus improving optical efficiency.
(b) Description of the Related Art
An organic light emitting diode (“OLED”) display has recently been gaining popularity among flat panel displays because of its low driving voltage, light and thin construction, wide viewing angle, and high-speed response. The OLED display is classified into a passive matrix type and an active matrix type depending on the driving method used therefor.
The active matrix type OLED display, in which thin film transistors (“TFTs”) are connected to each pixel region, controls the light emission of organic light-emitting layer on the basis of each pixel region. Pixel electrodes, each of which is electrically separated from adjacent other pixel electrodes to allow for independent control of each pixel, are located in each pixel region. In addition, walls, which are constructed on a substrate to be taller than the pixel electrodes, are formed between the pixel regions and serve to prevent a short-circuit between the pixel electrodes and to insulate between the pixel regions. A hole injection layer and an organic light-emitting layer may be sequentially formed on the pixel electrode between the walls. A common electrode is formed on the organic light-emitting layer.
Another way in which OLED displays may be differentiated is the orientation in which they emit light. There are two basic orientations; top-emission type and bottom-emission type. The top-emission type display emits light from the organic light-emitting layer through a common electrode to an outside. The bottom-emission type display emits light from the organic light-emitting layer through a substrate to an outside.
However, the OLED display has low external quantum efficiency, sometimes less than 20%, regardless of the light emission type. Also, the OLED has low optical efficiency since a portion of the light emitted by the light-emitting layer is emitted to the sides of the display and dissipated therefrom instead of being directed to the outside.